JPL scientist: Industrialization likely caused end of Little Ice Age

A team of researchers led by a Jet Propulsion Laboratory scientist may have cracked a cold case — quite literally — involving the rapid loss of glaciers in the 1860s.

Thomas Painter, a snow and ice scientist at JPL, joined scientists from UC Davis, University of Colorado and the University of Michigan in conducting the study. The team theorizes the soot and black carbon emissions from a booming, industrialized Europe in the 1860s attached to the glaciers in the European Alps, absorbing heat from the sun and causing them to rapidly retreat, or lose mass. The Industrial Revolution began in England in 1760 and lasted until around 1850.

“Scientists have thought the glacial retreat came from natural climatic anomalies along the way,” Painter said, “and yet this shows it’s very likely not a climate anomaly, but human particulate emission.”

Painter and his colleagues studied historical data of carbon particles trapped in the ice cores at the European mountain glaciers, determining how much black carbon was in the atmosphere and snow when the glaciers began to retreat at the end of the Little Ice Age, a cooler period between the 14th and 19th centuries when mountain glaciers expanded amid dropping temperatures.

The team studied computer models of glacier behavior that combined recorded weather conditions and the impact of pollution. The model’s glacier mass loss and timing were consistent with the historical records of glacial retreat during industrialization, despite cooling temperatures at the time, according to the study.

“It’s the same thing as if you were walking barefoot on the blacktop on a hot summer day,” said Waleed Abdalati, study co-author and director of the Cooperative Institute for Research and Environmental Sciences (CIRES) at the University of Colorado. “The blacker a surface, the more energy it’s absorbing, and that’s what this effect is.”

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The team’s research was published in the Proceedings of the National Academy of Sciences on Sept. 3. Georg Kaser, a glaciologist at the University of Innsbruck in Austria and lead author of the Working Group I Cryosphere chapter of the Intergovernmental Panel on Climate Change’s Fifth Assessment Report, co-authored the study.

“The paper is not designed to prove anything but provides a robust observation and model quantification based on hypothesis on the causes of the glacier retreat in the Alps from approximately 1850 onward, despite slightly falling air temperatures and constant precipitation amounts,” Kaser said via email. “We see a hypothesis as an essential tool in science and along this hypothesis we and others may now perform more detailed studies with the aim to either verify or falsify the hypothesis.”

Black carbon is the strongest sunlight-absorbing particle in the atmosphere, according to a news release. Whereas light-colored objects like snow refract light, the dark-colored soot that blew in from Italy and Germany and attached to the glaciers caused the glaciers to heat up and melt faster.

Painter’s studies in glacial melting started as unfunded research in 2004. After acquiring funding, Painter traveled to the Rocky Mountains and found the dark dust mixed in the snow absorbed sunlight faster, melting the snow. He combined his understanding of the Industrial Revolution with his research before coming to the conclusion that industrialization was most likely the cause of the glaciers’ retreat, he said.

“I’m baffled that no one has looked into it before,” Painter said. “And yet, a strong understanding of the impacts of black carbon really began in the last 15 years.”

Though the study examines the effects of soot and black carbon on centuries past, the phenomenon, which Abdalati called “the human fingerprint,” is still seen today, despite efforts to be more eco-friendly.

“It stands to reason that the same type of phenomenon we saw in the Alps, but on a different scale, is probably at play in the Artic,” Abdalati said. “It stands to reason that some of the stuff we put in the atmosphere falls on the snow.”

Soot and black carbon emissions today specifically impact countries like India, an industrially growing area that is “passing carbon back and forth,” Painter said.